The prior art has recognized the potential of sphagnum moss material for use as an absorbent medium in structures for absorbing body exudate. Sphagnum moss has highly desirable liquid-absorption properties such as a remarkable absorption capacity and the ability of desorbing adjacent materials by continuing to pull or wick liquid away from them over a long time period such that virtually all the liquid is collected in the sphagnum moss core. These attributes allow the material to provide highly efficient absorbent components which can be made relatively thin for better fit, comfort and discretion, while being sufficiently absorbent to prevent overflow leakage and garment staining.
The following U.S. patents document the use of sphagnum moss material for manufacturing absorbent components for disposable absorbent products:
______________________________________ U.S. Pat. No. INVENTOR DATE ISSUED ______________________________________ 4,170,515 Lalancette at al. Oct. 9, 1979 4,215,692 Levesque Aug. 5, 1980 4,226,237 Levesque Oct. 7, 1980 4,305,393 Nguyen Dec. 15, 1981 4,473,440 Ovans Sept. 25, 1984 4,507,122 Levesque March 26, 1985 4,618,496 Brasseur Oct. 21, 1986 4,676,871 Cadieux et al. June 30, 1987 4,992,324 Dube Feb. 12, 1991 5,053,029 Yang Oct. 1, 1991 ______________________________________
The subject matter of these patents is incorporated herein by reference.
Sphagnum moss material for use in manufacturing absorbent components is harvested from a sphagnous bog and transported to the processing site where it is refined and converted into a structurally integral continuous sheet. In sheet form, the sphagnum moss material can be conveniently rolled-up for storage and transportation and it is suitable for direct processing in the high speed automatic equipment that is currently used by the industry for assembling multi-layer disposable absorbent products.
Broadly stated, the process for converting raw sphagnum moss into a structurally integral continuous sheet begins with forming the raw material into an aqueous slurry that is wet classified to extract from the particle suspension the extremely fine particles, commonly referred to as fines, and large pieces of material including roots, branches and the like that do not significantly contribute to the absorbency of the final product. The refined slurry is sheeted on a Fourdrinier wire, dewatered and dried. The resulting structurally integral sheet is calendered to diminish the average pore size of the network in order to increase its drying power.
The prior art also suggests to employ additives for improving certain characteristics of the structurally integral sheet. In particular, the sphagnum moss can be treated with wetting agent in order to develop a superior affinity for aqueous liquids. Polyester fibers can be integrated into the sphagnum moss matrix to increase its resistance. These examples illustrate the variety of possible treatments that have a common objective to improve the liquid-absorption and the mechanical properties of the structurally integral sheet.
One area of the structurally integral sheet that has not yet been explored for the purpose of further improving its liquid-absorption properties is the composition of the sphagnum moss material. A better understanding of the relationship between absorbency and the composition of this vegetal absorbent medium is highly desirable to enable the manufacture of sanitary products having largely improved absorbent properties.